Footwear such as athletic footwear often has a midsole which is formed of two or more components. The midsoles are typically formed in molds, which require complex shapes in order to form a desired profile. The formation of a midsole having multiple components historically has required two separate molds, each having a complex shape matching the entire midsole, leading to increased manufacturing complexity and costs. Each half shoe size has typically required a different set of molds as well, leading to increased costs.
The footwear may contain an insert, such as a fluid filled bladder, which is disposed in a hollow area or cavity formed in the heel region of the midsole, to provide additional cushioning. In certain footwear midsoles, the insert is visible from the exterior of the article of footwear through apertures provided in the exterior of the midsole. To form footwear with an insert, a first portion of the midsole, typically made from a compressed EVA foam material such as Phylon, is formed in a fully shaped mold. Apertures are then cut through the side walls of the first portion. The formed first portion is placed in a second fully shaped mold, an insert is placed in the cavity formed in an area, such as the heel, of the first portion, a secondary material such as polyurethane is poured onto the first portion over the insert, and the secondary material is then cured. Having a second fully shaped mold is expensive and requires a complete refabrication of the second mold when a different sized midsole is desired, or when the location or size of the viewing aperture is changed.
The molds used to form such midsoles are desirably made with tight seals to reduce blow by of excess poured material when the mold is closed. Blow by, when used herein, is a term used to describe the seepage of poured material through gaps in the mold into regions where the material is not desired. Material that blows by becomes attached to the periphery of the midsole and must be removed by trimming, which is labor intensive, thereby increasing manufacturing costs as well. Over time the molds tend to settle or become worn, which increases the possibility of blow by and the subsequent need for trimming and cleaning the midsoles.
It is an object of the present invention to provide a method and apparatus for molding components for articles of footwear which reduce or wholly overcome some or all of the aforesaid difficulties inherent in prior known devices. Particular objects and advantages of the invention will be apparent to those skilled in the art, in view of the following disclosure of the invention and detailed description of certain preferred embodiments.